Greece moved to check the growing strains on its crippled financial system on Sunday, closing its banks and imposing capital controls that brought the prospect of being forced out of the euro into plain sight.

After bailout talks between the leftwing government and foreign lenders broke down at the weekend, the European Central Bank froze vital funding support to Greece's banks, leaving Athens with little choice but to shut down the system to keep the banks from collapsing.

Banks are expected to be closed all next week, and there will be a daily 60 euro limit on cash withdrawals from cash machines, which will reopen on Tuesday. Capital controls are likely to last for many months at least.

"The more calmly we deal with difficulties, the sooner we can overcome them and the milder their consequences will be," a somber-looking Prime Minister Alexis Tsipras said in a televised address. He promised bank deposits would be safe and salaries paid.

Even as Tsipras spoke, the lines forming at petrol stations and in front of the shrinking number of bank machines that still contained cash highlighted the scale of the disaster facing Greeks, who have endured more than six years of economic decline.

The failure to reach a deal with creditors leaves Greece set to default on 1.6 billion euros of loans from the International Monetary Fund that fall due on Tuesday. Athens must repay billions of euros to the European Central Bank in the coming months.

The impending default on the IMF loans leaves Greece sliding toward a euro exit with unforeseeable consequences for Europe's grand project to bind its nations into an unbreakable union by means of a common currency. It also carries broad implications for the global financial system.